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When a device is performing an operation, all other devices in the chain must be put into bypass. These global commands specify the number of bits to pad the beginning and end of an instruction; this cuts down on the overhead needed to put the other devices in bypass, because the padding does not need to be specified for each SIR or SDR instruction. As the number of devices in the chain increases, the advantage of using these global commands is much more significant.

For example, the "get device ID" of Device-1 for JTAG Programmer would be: